Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for transmitting data for a half-duplex device in a Frequency Division Duplex (FDD) system.
Related Art
3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is an improved type of a Universal Mobile Telecommunication System (UMTS) and is introduced as 3GPP release 8. 3GPP LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in downlink and uses Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink. 3GPP LTE-advanced (LTE-A), that is, an advanced type of 3GPP LTE, is recently being discussed.
A communication channel between a base station and a terminal is basically divided into a downlink (DL) channel from the base station to the terminal and an uplink (UL) channel from the terminal to the base station.
In 3GPP LTE and LTE-A systems, a method of transmitting data includes a Frequency Division Duplex (FDD) method and a Time Division Duplex (TDD) method. The FDD method means that uplink transmission and downlink transmission are performed at the same time while occupying different frequency bands. The TDD method means that uplink transmission and downlink transmission are performed at different times while occupying the same frequency band.
In order for a terminal to perform uplink transmission and downlink reception at the same time, the terminal needs to have a full-duplex capability. A terminal incapable of performing uplink transmission and downlink reception at the same time is called a half-duplex device compared to a full-duplex device. The half-duplex device is advantageous in that it has low hardware complexity and has a low price compared to a full-duplex device. In particular, a half-duplex device is advantageous in terms of the price if the size of transmitted and received data is not great and the size of transmitted data is much greater than that of received data as in a Machine Type Communication (MTC) device.
In order for a half-duplex device to efficiently use radio resources, however, a base station is required to schedule radio resources so that the half-duplex device does not perform uplink transmission and downlink reception at the same time. In the FDD method of 3GPP LTE and LTE-A systems, a terminal is assumed to basically have a full-duplex capability, which may be additional scheduling overhead to a base station. In particular, if the number of half-duplex devices served by a single base station is many, a scheduling overhead problem may become serious. Accordingly, there is a need for a method of scheduling resources, which supports a half-duplex device, which is more flexible, and which has low overhead.